Particle throwing apparatus



Dec. 13, 1966 J. E. BOWLING, JR.. ETAL 3,290,827

PARTICLE THROWING APPARATUS Original Filed April 27, 1962 4 Sheets-Sheet 1 v N g In INVENTORS Joseph EBowZm Gem ge W Powe ATTORNEYS Dec. 1965 J. E. BOWLING, JR, ETAL 3,290,327

PARTICLE THROWING APPARATUS 4 SheetsSheet 2 Original Filed April 27, 1962 INVENTORS JOSqphE BowZin gaJac i ATTORNEYS INVENTORS Dec. 13, 1966 J. E. BOWLING, JR.. ETAL 3,290,827

PARTICLE THROWING APPARATUS Original Filed April 2'7, 1962 4 Sheets-Sheet a Jose hEBowZin J11, Gemy e W Powcl By ww/lg ATTORNEY Dec. 13, 1966 J. E. BOWLING, JR.. ETAL v3,290,327

PART I OLE THROWI NG APPARATUS 4 Sheets-Sheet 4 Original Filed April 2'7, 1962 INVENTORS Jose phi. 230w Geoge WT BY ATTORNEYS United States Patent 3,290,327 PARTECLE THROWING APPARATUS loseph E. Bowling, .ln, Waynesboro, Pa., and George W. Powell, Hagerstown, Md., assignors to The Pangborn (Iorporation, Hagerstown, Md, a corporation of Delaware Original application Apr. 27, 1962, Ser. No. 190,725. Divided and this application Feb. 11, 1965, Ser. No.

12 Claims. (6]. 51-9) This application is a division of copending application Serial No. 190,725, filed April 27, 1962, now abandoned, which in turn is a continuation-in-part of application Serial No. 753,530, filed August 6, 1958, now abandoned.

The present invention relates to a particle throwing apparatus, in particular to such an apparatus of the type shown in US. Patent 2,732,666, granted January 31, 1956. Such apparatus forcefully projects a directional stream of particles for impingement against work pieces that are to be cleaned, peened or otherwise treated by the articles.

Among the objects of the present invention is the provision of novel constructions for such apparatus so that they are simpler and more reliable to use and maintain.

The above as well as additional objects of the present invention will be more clearly understood from the following description of several of its exemplifications, reference being made to the accompanying drawings wherein:

FIG. 1 is a partially sectional vertical view of the principal portion of a particle throwing device in accordance with the present invention;

FIG. 2 is a section taken along line 2 of FIG. 1;

FIG. 3 is a section taken along line 33 of FIG. 2;

FIG. 4 is another view of the wheel portion of the apparatus of FIG. 1, partially in section with additional cooperating structures shown;

FIG. 5 is a broken-away front view .of the construction of FIG. 4, taken from the right of FIG. 4;

FIG. 6 is a detail on an enlarged scale of the construction of FIGS. 4 and 5; and

FIG. 7 is a broken-away perspective in section of another form of throwing apparatus.

Turning now to the drawings, the combined particle throwing assembly according to one form of the invention, is here shown as having a spindle 10 (see FIG. 1) journaled in a tubular support 12 as by bearings 13, 14.

The spindle is arranged to be rotated as by means of a pulley 15 on one end in the manner shown in US. Patent 2,732,666.

At its other end, the spindle is provided with a radially enlarged flange 16 clamped, shrunk, keyed, or otherwise securely held in place. The rot-or or runner head, which is illustrated at 18, is in turn secured to the front face of flange 16, by bolts in the rotor and threadedly engaged in the flange.

A plurality of vanes 40 is secured to the exposed face 42 of the rotor, as by having one edge 22 of each vane provided with a dovetail 24 (see also FIGS. 2 and 4) that is received in a mating groove 26 in the rotor. A central feed space 28 (FIG. 4) is provided in the central region between the inner ends of the vanes.

The usual type of central impeller 62 is secured coaxially with the rotor as by means of bolt 64 and has a number of spaced impeller bars 66 positioned in feed space 28. Between the impeller and the inner ends of the vanes a generally cylindrical impeller case or particle directing cage 70 is adjustably secured, and in the illustrated construction has its outer end open and provided with an outwardly flanged lip 72 seated against a housing 75 that covers the vanes, rotor and adjacent portion of the spindle 10. The housing is secured to the spindle support 12 as by bolts, not shown, and completely sur- 3,290,827 Patented Dec. 13, 1 966 rounds the assembly except for an opening 77 (FIG. 1) through which a portion of the wheel can project, and also through which the projected particles are thrown. The direction of such projection is controlled by a slot 79 in the impeller case. This slot, which can be rectangular, triangular, etc., is confined to a limited portion of the cages periphery, as is well known.

A deflector ring 60 (FIG. 4) can also be fitted against the face 22 of the rotor, and can be held in place as by screws 61. This deflect-or ring causes any abrasive particles that might escape through the rot-or end of the impeller case to be deflected onto the outer face 42 of the rotor as well as against throwing faces of the vanes and thus prevents excessive wear of the vane-receiving grooves 26.

The housing can, as illustrated, have a front wall 81 and a back wall 82, as well as side walls 84, and a top wall that is not illustrated. Front wall 81 is shaped to fit under the impeller case lip 72, as by recess 86. An opening in the housing through which the impeller cage penetrates also receives spout 88 which forms part of the particle supply mechanism and is arranged to deliver these particles to the interior of the impeller 62 where they can be moved by the impeller bars 66, and thus thrown through the cage slot 79. Spout 88 is held against the open end of cage 70, and a circular flange 92 around the rear end of the spout can cover and seal the entire open cage end. An internal shoulder 73 on the internal surface of lip 72 provides an effective engagement site, and a readily deformable sealing ring or gasket 90 (FIG. 4) can also be used as part of the seal between the flange 92 and lip 72.

The spout 88 is conveniently held in place by a readily releasable clamp shown (see FIGS. 4, 5 and 6) as a bail 99 pivotally mounted at 97 on front housing wall 81 on both sides of the spout, which bail carries a clamping screw 94. This screw 94 is arranged to engage a socket 96 on a boss 98 formed on the spout so as to lie on or near the axis of the circular flange 92. The clamping screw is threaded through an insert 98 in the cross arm of the bail as by providing an enlarged socket 100 in the arm, threading the insert into the socket and locking it there with a jam nut 102.

To keep from turning the clamping screw 94 through many revolutions when clamping or unclamping, the threaded passageway 104 through insert 100 is intersected by a larger unthreaded passageway 106 at a small angle, so that the mere loosening of the screw by as little as one or two turns will enable the screw to be tilted into the unthreaded passageway and thus retracted out of the way. For returning it to clamping engagement, the steps are retraced. When disengaged, the clamp hangs down completely free of the spout as well as the impeller case 70. The spout can then be pulled out slightly and the impeller case shifted in rotary position when it is desired to change the direction of the stream of particles discharged from the wheel. The spout can then be returned to its proper place and the clamp resecured.

The plane in which the clamp screw is tilted to move between the passageways 104, 106 is illustrated as horizontal, that is, parallel to the pivot axis for the bail 99. In other words, the screw tilting is horizontal and the bail movement vertical sothat unintended slight loosening of the screw will not tend to permit the bail to drop. Even if the screw tilts a small amount such tilting will be at right angles to the direction in which the bail tends to move the screw, so that the bail will remain clamped in place.

An indicator ring (FIGS. 4 and 5) is fitted to housing wall 81 around the cage lip 72, as by screws 107, and carries fingers 109 that overlie the lip, thereby keeping the cage from slipping out too freely. Notches 109 in the lip margin permit cage removal after the notches are aligned with the fingers. Sometimes the cage may be diflicult to rotate because it is jammed or stuck in position. A groove 103 extending completely across the open face of lip 72 provides a very effective site against which a jarring tool such as a chisel can be engaged and hammered for the purpose of loosening and turning the cage when it is so jammed. A single groove of this kind is all that is needed because it is readily accessible once the spout is removed, and the spout must be disengaged before the case is free to rotate. The groove 103 can be used as a locating indicator, or if desired some other marker, such as a cast-in pointer, can be so used in conjunction with scale markings that can be provided around the indicator ring 105.

The inside ofvthe housing can be lined with wear resistant material. A front liner is shown at 120, and a rear liner at 112.

The front, rear and side liners are very effective in helping guard against particles bouncing off in undesired directions, and for maximum effectiveness can be projected out beyond the open end 77 of the housing, and in fact, beyond the limits of the rotor and even of the vanes. To keep the projected particles from working their way into undesired places, particularly the bearings for the spindle 10, the apparatus of FIG. 1 is shown as having a succession of seals as well as a baffle. The central section of rear liner 112 is, in this construction provided with a cylindrical baffle flange 150 that projects forwardly and s spaced from the periphery of rotor 18. Baflie flange 150 does not entirely keep particles from finding their way into space 151 between the rotor and the rear liner. It does, however, keep the most vigorously projected particles from being forcefully directed into this space and this reduces wear of the rotor. In fact, it is desirable to provide the baffle flange 150 with one or more openings, as indicated at 152, at or near its lowermost portion for particles in this chamber to drop out. The openings 152 are preferably tapered in order to reduce the possibility that the flying particles find their way inwardly into the chamber through this discharge opening.

A sealing ring 156 is loosely provided on to the spindle or rotor housing and protects the bearings. It preferably extends in close relationship (not more than about inch away) with the spindle flange 16 which can also have a cooperating lip 158 at its periphery projecting rearwardly to overlap the forward margin of the sealing ring 156. Again a spacing of about A inch is all that should be permitted between the lip 158 and the adjacent surface of the sealing ring. It has been found that a groove such as one of circular cross-section as indicated at 160, if cut in the sealing ring 156 in the space between lip 158 and the spindle housing, greatly helps in keeping particles from working their way into and through the very close space between the sealing ring 156 and the spindle flange 16. It seems that particles moving toward the surface of groove 160 tend to be channeled around the ring and drained away so that only very few will reach the small gap provided by the above small spacing.

However, some particles, and particularly the dustlike particles, will work their way through eventually, and these particles are highly injurious to the life of the bearings. A second sealing ring 166 is therefore shown in FIG. 1 as secured to the spindle housing 12 and extending into closely spaced relation with the inner portions of the spindle flange 16. Ring 166 is also shown as provided with a relatively extensive sealing surface, as by shaping its central portions into a cylinder 168 and by giving the forward edge of the cylinder an outwardly turned lip 170. Lip 170 is in close mating engagement with a lip 172 in the rear face of the central portion of flange 16. The cylindrical portion 168 of sealing ring 166 can be similarly closely engaged with the spindle or, as shown in the drawing, with a collar 174 mounted on the spindle. The spacing of the second ring from its cooperating surface also can be held down to about i inch or even less. Shall-ow spaced grease grooves 176 can be cut in the sealing surface of the cylindrical portion 168 to form a grease seal. A spacing of about an inch between the rings 156 and 166 is particularly desirable, as is also shown locking washer 169, prevents movement of collar 174 on the spindle threads.

The above combination of seals, rings and baffle has been found extremely effective, particularly if the spindle bearings are lubricated regularly as by means of externally opening lubrication passages. The lubricant, which is preferably a relatively heavy grease, is introduced under pressure and tends to work its way into the small clearance between the sealing ring 166 and the adjacent portions of the spindle and flange, thus providing an additional barrier to the ingress of solid particles into the spindle bearing compartment.

The drive end of the spindle 10, where it emerges from tube 12, can also be sealed against penetration of particles, as by a similar sealing ring 171. As illustrated in FIG. 1, the spindle bearings can each have sets of lubrication openings leading to different portions of the bearings so as to provide more thorough lubrication as well as a good flushing action to flush out old contaminated lubricant as fresh lubricant is introduced.

In the construction of FIG. 1 the spindle flange 16 has an internal opening 30 which is tapered and is fitted over a bushing 31 that has an outer surface provided with a mating taper. The inner surface of the bushing 31 can be cylindrical to fit against a correspondingly shaped portion of the spindle.

The tapered bushing 31 is made of springy metal and has a split, which is not illustrated in the drawing, at one portion of its periphery. The split extends the entire axial length of the bushing and the edges on each side of the split are spaced apart so that they can be brought together when the bushing is forced into a restricted socket. The bushing also has an enlarged head 33 through which screws 34 can be fitted so that the bushing can be forcefully drawn against flange 16. For this purpose unthreaded holes 35 are located in the bushing head 33 and threaded holes 36 in corresponding portions of the flange. The parts are so dimensioned that drawing up on the bolts 34 forces the bushing into the tapered opening 30 of the flange and causes the split bushing ends to approach each other, thereby clamping the cylindrical internal face of the bushing against the spindle. To assure a reliable non-slip clamping engagement, key 37 can be fitted between keyways in the spindle and bushing respectively. No keying is needed at the tapered joint between surfaces 30 and 32, and the key 37 need not be used except in wheel constructions that are subjected to extreme stresses.

The impeller 62 has a hollow cylindrical body whose cylindrical walls need not be more than about /2 inch thick. By making these walls thin more space is provided within the impeller and the flow of particles through the vanes is increased. As shown in FIG. 4 the edge 63 of slots 65 between the successive bars 66 of the impeller is cut away so that the slots flare outwardly toward the rotor 18. This flared arrangement effectively distributes the abrasive on the vanes.

The wall 67 closing the rotor end of the impeller includes an outwardly offset boss 69 which enables recessing of the head of screw 64. The distance between the outer edge of boss 69 and the outer faces of the impeller bars 66 is preferably about 1 /2 inches to give very effective reduction of leakage of the abrasive particles. For

this purpose the impeller cage has its end wall 82 correspondingly extended close to the boss 69. A slight lip 83 projecting out radially from the boss beyond the location where the cage end wall 82 approaches it, helps keep stray particles directed over the face of the deflector ring. The impeller and rotor are aligned by mating sockets 87 (FIG. 3) and lugs. Such alignment is used to position the impeller so that the advancing edges 89 of the impeller bars 66 (see FIG. 2) are between 5 and preferable 10, ahead of the advancing faces 91 of the vanes. The direction of rotation is shown in this figure by the arrow 41.

It has also been discovered in accordance with the present invention that it is much more advantageous to have the bolt 64 holding the impeller only secured to an easily replaced insert or bushing, as shown at 190. This insert is conveniently received by a socket 192 formed in the body of the rotor 18 in alignment with the passageway 194 through which the bolt penetrates the rotor. The bushing 190 does not have to be a force fit and it is preferably arranged so that it can be fairly readily removed and replaced.

It is also desirable to have the side edges of the cage slot 79 arranged so that one of them, 80, is essentially in a radial plane, while the other, 59, is flared outwardly, as indicated in FIG. 2. The flared edge 59 is the edge towards which the blastant particles are propelled by the impeller bars 66, and improves the impelling action while at the same time permits greater throughput of blastant. The amount of flaring can be from about 10 to 60.

In the above construction the vanes (40) are wedged in place in the respective rotor grooves 26 (FIGS. 1-4). Near the outer end of each groove the floor has a first recess 22 (FIG. 4) which is fairly shallow, and a second recess 24- which is deeper. A dam 17 just beyond the second recess is at floor level, and is cut by a channel 19 into two portions. The side walls 21 (FIGS. 2 and 3) of the grooves are shown as of dovetail shape except that near the outer end these walls are relieved as illustrated at 23 (FIG. 1).

The vanes are held in the grooves by gibs 38 (see FIG. 4) that have a springy tail 25 secured as by brazing to a wedge block 27 of triangular cr0ss-section. The outer end of the dovetail flange on the vane has a wedge face 29 that engages a corresponding wedge face of the gib and jams the outer end of the gib against the dam 17, under the influence of the centrifugal force developed by the rotation of the wheel. Mounting of the vanes is effected by sliding a vane into its groove, and then slipping the gib in under it. The vane is arranged to move into its groove about inch further than the illustrated wedge position, so that the block on the outer end of the gib can be inserted after the vane. After the gib is in place the vane is pulled'out into wedged position, and the springy tail of the gib squeezed between the floor of the groove and the bottom of the vanes mounting flange keeps the vane wedged. Removal of a vane is accomplished in the reverse manner. The vane is driven inwardly as by hammering, to provide the above clearance for the gib. A straight tool like a screw driver blade can then he slipped through'the slot 19 to force the Wedge block up over the darn 17. Both the vane and the gib are then withdrawn.

In the modification shown in FIG. 7 spout 288 is illustrated as held in place against the impeller cage 270 by a quick-acting toggle clamp 293, while one or more additional quick-acting toggle clamps 295 lock the lip of the cage to the housing. Removal of the spout only requires operation of clamp 293, but adjustment of the cage calls for manipulation of all the clamps. Manually operated clamps of this type are, however, simple and rapid to operate.

Obviously, many modifications and variations of the present invention are possible in the rlight of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than-as specifically described.

What is claimed is:

1. A throwing wheel for blasting articles with particles, said wheel having a rotor carrying radially directed vanes for centrifugally throwing outwardly abrasive particles that are fed to the inner portions of the vanes; a journaled spindle on one end of which the rotor is mounted for rotation; a radial flange on said spindle end; a housing covering the rotor, flange and the adjacent portions of the spindle, a first sealing ring held within the housing adjacent the inner portion of the flange face opposite to that engaged by the rotor, said ring extending toward the flange, a mating groove in the flange receiving the extending portion of the ring and closely spaced therefrom, a second sealing ring encircling but spaced from the first sealing ning and held by the housing adjacent the outer portion of the flange, the flange having a peripheral lip projecting into closely spaced cooperation with the outer face of the second sealing ring, the lip being more widely spaced from the housing and the second sealing ring having its outer surface grooved in the portion exposed by the last-mentioned spacing.

2. A throwing wheel for blasting articles with particles, said wheel having a rotor carrying radial-1y directed vanes for centrifugally throwing outwardly abrasive particles that are fed to the inner portions of the vanes, the vanes extending short of the rotors center and defining a central chamber, a cylindrical feed cage positioned within said chamber coaxially with the rotor and having an inlet opening in its outer face and a discharge slot in its periphery, an impeller within the cage and connected for rotation with the rotor, a housing encircling the rotor, cage and impeller, and having an opening aligned with the cage, the housing carrying a readily releasable clamping mechanism, a spout held by the clamping mechanism in the housing opening and in communication with the cage inlet, the spout having elements engaging the cage and automatically anchoring the cage to the housing when the clamping mechanism holds the spout in place, and the readily releasable clamping mechanism being a toggle clamp.

3. A throwing wheel for blasting articles with particles, said wheel having a rotor carrying radially directed vanes for centrifugally throwing outwardly abrasive particles that are fed to the inner portions of the vanes, the vanes extending short of the rotors center and defining a central chamber, a cylindrical feed cage positioned within said chamber coaxially with the rotor and having an inlet opening in its outer face and a discharge slot in its periphery, an impeller within the cage and connected for rotation with the rotor, a housing encircling the rotor,

cage and impeller, and having an opening aligned with the cage, the housing carrying a readily releasable clamping mechanism, a spout held by the clamping mechanism in the housing opening and in communication with the cage inlet, the spout having elements engaging the cage and automatically anchoring the cage to the housing "when the clamping mechanism holds the spout in place,

the readily releasable clamping mechanism including a clamping screw threaded through a quick-release bushing carried on a bracket pivoted on the housing, and the quick-release bushing having its threaded passageway intersected by a second passageway wide enough to pass the shank of the screw without threading.

4. The combination of claim 3 in which the passageways define a plane parallel to the axis on which the bracket is pivoted.

5. A throwing wheel for blasting articles with particles, said wheel having a rotor carrying radially directed vanes for centrifugally throwing outwardly abrasive particles that are fed to the inner portions of the vanes, the vanes extending short of the rotors center and defining a central chamber, a cylindrical feed cage positioned within said chamber coaxially with the rotor and having an inlet opening in its outer face and a discharge slot in its periphery, an impeller within the cage and connected for rotation with the rotor, a housing encircling the rotor, cage and impeller, and hiauing an opening aligned with the cage, the housing carrying a readily releasable clamping mechanism, a spout held by the clamping mechanism in the housing opening and in communication with the cage inlet, the spout having elements engaging the cage and automatic-ally anchoring the cage to the housing when the clamping mechanism holds the spout in place, the housing carrying retaining finger means overlying the outer rim of the cage, and said outer cage rim being notched to enable withdrawal of the cage when its notching is aligned with the finger means.

6. A thr-owing Wheel for blasti-ng articles with particles, said wheel having a rotor carrying radially directed vanes for centrifugally throwing outwardly abrasive particles that are fed to the inner portions of the vanes, the vanes extending short of the rotors center and defining a central chamber, a cylindrical feed cage positioned within said chamber coaxially with the rotor and having an inlet opening in its outer face and a discharge slot in its periphery, an impeller within the cage and connected for rotation with the rotor, a housing encircling the rotor, cage and impeller, and having an opening aligned with the cage, the housing carrying a readily releasable clamping mechanism, a spout held by the clamping mechanism in the housing opening and in communication with the cage inlet, the spout having elements engaging the cage and automatically anchoring the cage to the housing when the clamping mechanism holds the spout in place, said rotor being journale'd on one end of a spindle; a radial flange on said spindle end; a housing covering the rotor, flange and the adjacent portions of the spindle, a first sealing ring held within the housing adjacent the inner portion of the flange face opposite to that engaged by the rotor, said ring extending toward the flange, a mating groove in the flange receiving the extending portion of the ring and closely spaced there-from, a second sealing ring encircling but spaced from the first sealing ring and held by the housing adjacent the outer portion of the flange, the flange having a peripheral lip projecting into closely spaced cooperation with the outer face of the second sealing ring, the lip being more widely spaced from the housing and the second sealing ring having its outer surface grooved in the portion exposed by the lastmentioned spacing.

7. A throwing wheel feed cage having a cylindrical body with a slot extending along its side wall, said body having one end open, and an outwardly turned lip extending around said open end, the lip forming an internal shoulder for engagement by a feed spout, and the lip also having its outer rim notched through so that the cage can be moved in an axial direction past retaining finger means aligned'with the notching, but cannot be moved back past the retai-ning finger means when it is not aligned with the notching. I

8. The combination of claim 7 in which the slot extends in an axial direction to the end wall of the body, one side edge of the slot has a face lying in a plane in which the cylindrical axis also lies, and the opposite 8 side edge of the slot is flared outwardly, said body end wall has a central opening and extends about 1 /2 inches from the edge of the opening to the cylindrical wall, and the lip has a single recessed groove extending completely across its outer face.

9. A throwing wheel impeller having a generally cylindrical body with a cylindrical wall not more than about /2 inch thick, said cylindrical wall being perforated around its periphery by a plurality of spaced axially extending slots, one end of the-body being open, an end wall across the other end of the body, radially directed grooves in the end wall alongside the slots to flare the slot ends outwardly, and mounting elements including outwardly directed extensions on the end wall for securing the impeller to a wheel rotor and causing the impeller to rotate with the rotor.

10. The combination of claim 9 in which the mount ing elements include an outwardly olfset central boss in the end wall, said boss having an axial passageway for receiving a mounting bolt and holding the head of the bolt recessed with respect to the wall.

11. The combination of claim 10 in which the end wall extends radially about 1 /2 inches from the outside surface of the boss, and said outside surface has a radially outwardly projecting lip spaced from the end wall.

12. A throwing wheel spout having near one end an encircling shoulder for gasketed engagement with an impeller cage, and having near its other enda clamping boss with a clamp-receiving recess located along the axis around which the shoulder extends.

References Cited by the Examiner UNITED STATES PATENTS 2,108,006 2/1938 Keefer 51-9 2,135,550 11/1938 Alexander 51-9 2,170,831 8/1939 Minich 51-9 2,170,832 8/1939 Minich 51-9 2,204,587 6/ 1940 Guendling 51-9 2,261,228 11/1941 Cockrum 76-101 2,306,847 12/ 1942 Turn-bull 51-9 2,341,560 2/ 1944 Keefer 51-9 2,352,588 6/1944 Rosenberger et a1. 51-9 2,368,664 2/ 1945 Keefer 51-9 2,708,814 5/1955 Straub 51-9 2,732,666 1/ 1956 Powell 51-9 2,819,562 1/1958 Barnes 51-9 2,869,289 1/ 1959 Gossard 51-9 2,983,082 5/1961 Gossard 51-9 FOREIGN PATENTS 1,232,124 4/ 1960 France.

LESTER M. SWINGLE, Primary Examiner. 

1. A THROWING WHEEL FOR BLASTING ARTICLES WITH PARTICLES, SAID WHEEL HAVING A ROTOR CARRYING RADIALLY DIRECTED VANES FOR CENTRIFUGALLY THROWING OUTWARDLY ABRASIVE PARTICLES THAT ARE FED TO THE INNER PORTIONS OF THE VANES; A JOURNALED SPINDLE ON ONE END OF WHICH THE ROTOR IS MOUNTED FOR ROTATION; A RADIAL FLANGE ON SAID SPINDLE END; A HOUSING COVERING THE ROTOR, FLANGE AND THE ADJACENT PORTIONS OF THE SPINDLE, A FIRST SEALING RING HELD WITHIN THE HOUSING ADJACENT THE INNER PORTION OF THE FLANGE FACE OPPOSITE TO THAT ENGAGED BY THE MOTOR, SAID RING EXTENDING TOWARD THE FLANGE, A MATING GROOVE IN THE FLANGE RECEIVING THE EXTENDING PORTION OF THE RING AND CLOSELY SPACED THEREFROM, A SECOND SEALING RING ENCIRCLING BUT SPACED FROM THE FIRST SEALING RING AND HELD BY THE HOUSING ADJACENT THE OUTER PORTION OF THE FLANGE, THE FLANGE HAVING A PERIPHERAL LIP PROJECTING INTO CLOSELY SPACED COOPERATION WITH THE OUTER FACE OF THE SECOND SEALING RING, THE LIP BEING MORE WIDELY SPACED FROM THE HOUSING AND THE SECOND SEALING RING HAVING ITS OUTER SURFACE GROOVED IN THE PORTION EXPOSED BY THE LAST-MENTIONED SPACED. 